Wow Kristin! That sucks about your friends, but it seems like they will recover ok. I always hear stories about people crashing at Coral Pink. The biggest reason for it is like Paul Rob said- the drop offs are almost impossible to see in the middle of the day. When we go up there, we don't even ride during certain times of the day. If we do, we stay to the left side of the dune area where there are more trees and trails.
It still seems like you had fun despite your friends' accidents. I love that place.